A nonlinear model predictive control strategy for a wave-to-wire model of vibro-impact wave energy converters

In this study, the application of nonlinear model predictive control (NMPC) on a wave-to-wire (W2W) model of vibro-impact wave energy converters (VIWECs) is investigated. A nonlinear model predictive control strategy is proposed, for maximising wave energy capture and regulating the varying VIWEC power output as stable DC power. The optimal power take-off (PTO) force, viewed as a control input for maximising wave energy capture, is generated by the NMPC strategy, and actuated by a AC/DC converter with the space vector pulse width modulation (SVPWM) technique. In addition, a hybrid energy storage system (HESS), consisting of a battery and a supercapacitor, is integrated to the DC bus of the AC/DC converter via buck-boost DC/DC converters, and the DC bus voltage is stabilised by Lyapunov-based controllers, for providing stable and continuous power for DC payloads. Numerical results show that the performance of the W2W model with the proposed NMPC strategy is sensitive to sampling interval, prediction steps, current constraints and weight factors.